The etiology of the underlying immune deficiencies seen in acquired immune deficiency syndrome (AIDS) is unknown. Current observations suggest that a transmissible agent, possibly a virus, may be involved. A parvo-like virus has been suggested as the possible etiological agent for AIDS because a number of characteristics of AIDS are exhibited in the pathogenesis of individual members of the parvovirus family. Successful isolation of the AIDS agent will be difficult due to the large number of opportunistic infections present in AIDS patients. Therefore, it is essential to have access to clinical specimens obtained early in the course of AIDS. Commencing in the autumn of 1983, a large number of such samples collected prospectively by an NIAID intramural contract from several male homosexual populations in New York will be available for analysis. We propose to attempt to isolate the AIDS agent from specimens of semen, feces, and lympho-reticular cells. The minimum number of cell lines needed to support the widest range of viruses including defective and non-defective parvoviruses will be utilized in the isolation procedure. These lines will include human, simian, rodent, canine, and feline cells. Dual infection with species-specific adenoviruses and (where feasible) herpes viruses will also be carried out for possible induction of adenovirus-associated-like agent growth. Since the agent may exhibit limited or no cytopathic effect in tissue culture, and may replicate inefficiently or in an abortive fashion, the cultures will also be scored by IFA using pre, acute and convalescent sera from AIDS patients as the "driving" antibody, as well as a panel of known positive virus antisera.